|Oranges are a popular and relatively|
affordable fruit. It would be great if
claims that they kill parasites were
true. Image by Rosino: CC BY-SA 2.0
Antiparasitic Oranges - The Science
A search for papers on the antiparasitic properties of oranges yields very little, but when I looked at orange essential oil and parasites, I found some research. Studies have used orange oil to treat parasites in fish, sheep, gerbils, and in the lab, but none (at least none that I could find) have used human subjects.
A study by Squires and colleagues investigated whether an orange oil emulsion would kill a roundworm parasite in gerbils and sheep. These researchers found that, at a high enough dosage, the treatment killed a significant number of the worms, suggesting that it might be useful in animal parasite control.
In contrast, in a 1990 Japanese study, “many essential oils were found to be nematocidal to the larvae of dog-roundworm, Toxocara canis,” but essential oil of oranges wasn’t one of the star examples. In the lab, only about a third of larvae were killed by orange oil, and only after 24 hours of exposure.
Hirazawa and colleagues studied whether plant essential oils could be used to kill a flatworm that infests puffer fish. They looked at caprylic acid (derived from palm and coconut oil, and human milk), orange oil, peppermint oil, and cinnamon oil, exposing the parasites to the oils in the lab. The researchers found that orange oil is the only one of the four that does not affect this parasite.
Other studies found orange oil to be ineffective at killing honey bee mites, and ineffective at killing kissing bugs, the vector of Chagas' disease. So it looks like orange oil may kill some parasites, under specific conditions, but it’s no panacea. The good news is that it does appear to be useful, if used properly, in the control of subterranean termites.
Oranges vs Orange Essential Oil
Essential oils are derived from plants using a distillation process. They are highly concentrated essences, and orange oil is generally made from the peel of the fruit. Obviously, eating an orange is very different from ingesting orange oil (and I’m not sure that this would be safe). I wonder how many oranges one would have to consume (including the peel) to get any benefit, assuming you had a parasite that they would kill.
I believe it’s safe to say that there is no convincing evidence that orange oil is a good way to keep parasites at bay, and there is no evidence at all for oranges.
Hirazawa, N., T. Ohtaka, and K. Hata. 2000. “Challenge trials on the anthelmintic effect of drugs and natural agents against the monogenean Heterobothrium okamotoi in the tiger puffer Takifugu rigripes.” Aquaculture, 188, 2000
Nakamura N., F. Kiuchi, Y.Tsuda et al. 1990 "Nematocidal and bursting activities of essential oils on the larvae of Toxocara canis." Shoyakugaku Zasshi: 44(3).
Squires J., J. Foster, D. Lindsay et al. 2010. "Efficacy of an orange oil emulsion as an anthelminticagainst Haemonchus contortus in gerbils (Meriones unguiculatus) and in sheep." Am.Vet Parasitol. Aug 27;172(1-2):95-9. doi: 10.1016/j.vetpar.2010.04.017.